A fuel injector having a stepped spray-discharge orifice is described in German Patent Application No. DE 199 37 961 A1, for example. The spray-discharge orifice is divided into a through hole and a discharge-side or flow-off-side exit region, the exit region differing from the through hole in form, contour and size.
A particular disadvantage of the fuel injector described in the aforementioned printed publication is that, given a correspondingly broadened fuel jet emerging from the through hole, parts of the exit region may be directly exposed to the action of the fuel. In addition, in an exit region whose contour and size is similar to that of the fuel jet, no other volume remains in the exit region. As a result of both disadvantages, fuel remains in the vicinity of the discharge orifice after the spray-discharge operation since hardly any gas turbulence, which removes fuel from the region of the spray-discharge orifice once the injection process has been completed, is able to form. This can cause combustion deposits to form after a short operating time, which have a disadvantageous effect on the further operation of the fuel injector. In addition, the fuel residue that remains in the region of the spray-discharge orifice after the discharge operation increases the emission values and the fuel consumption.
Furthermore, it is impossible to fully adapt the length/width ratio and the fuel pressure to the various requirements of different internal combustion engines.